java.lang.IndexOutOfBoundsException
at java.nio.Buffer.checkIndex(Unknown Source)
at java.nio.DirectByteBuffer.get(Unknown Source)
at org.lwjgl.input.Keyboard.isKeyDown(Keyboard.java:407)
at com.darkona.adventurebackpack.client.gui.GuiAdvBackpack.func_73864_a(GuiAdvBackpack.java:228)
at net.minecraft.client.gui.GuiScreen.func_146274_d(GuiScreen.java:296)
at net.minecraft.client.gui.GuiScreen.func_146269_k(GuiScreen.java:268)
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1640)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:973)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:898)
at net.minecraft.client.main.Main.main(SourceFile:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

A detailed walkthrough of the error, its code path and all known details is as follows:
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-- Head --
Stacktrace:
at java.nio.Buffer.checkIndex(Unknown Source)
at java.nio.DirectByteBuffer.get(Unknown Source)
at org.lwjgl.input.Keyboard.isKeyDown(Keyboard.java:407)
at com.darkona.adventurebackpack.client.gui.GuiAdvBackpack.func_73864_a(GuiAdvBackpack.java:228)
at net.minecraft.client.gui.GuiScreen.func_146274_d(GuiScreen.java:296)
at net.minecraft.client.gui.GuiScreen.func_146269_k(GuiScreen.java:268)